Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 280955
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
355 AM MDT SAT MAR 28 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 354 AM MDT SAT MAR 28 2015

THE RIDGE WAS BREAKING DOWN AS IT MOVED OVERHEAD THIS EARLY
MORNING UNDER PRESSURE FROM A TROUGH MOVING THROUGH WASHINGTON-
OREGON. IN SPITE OF THE WEAKENING OF THE RIDGE...AFTERNOON
TEMPERATURES WILL SOAR TO 15-20 DEGREES ABOVE NORMAL. GUSTY PRE-
FRONTAL WINDS EXPECTED ESPECIALLY NORTH OF I-70 AS GRADIENT WINDS
INCREASE AND DEEP MIXING BRINGS THEM DOWN TO THE SURFACE. THE
TAIL OF THE WEAK COLD FRONT DROPS SOUTH OF THE WYOMING BORDER LATE
AFTERNOON AND THROUGH THE I-70 CORRIDOR IN THE LATE EVENING BEFORE
STALLING IN THE ABAJO-NW SAN JUAN MTNS TOWARDS SUNDAY MORNING.  MODELS
REMAIN IN GOOD AGREEMENT THAT THE FRONT WILL ONLY HAVE MARGINAL
MOISTURE TO WORK WITH...PRECIP WATER VALUES AROUND 0.4 INCH AND
700MB SPECIFIC HUMIDITY 3-4 G/KG. SO IT WILL TAKE THE ADDITION OF
LATE-DAY INSTABILITY TO SET OFF SHOWERS. THAT TOO IS MARGINAL
WITH CAPE VALUES IN THE 200-400 J/KG RANGE INTO THE EVENING.

EVENING ISOLATED SHOWERS FOLLOW THE FRONT INTO THE CENTRAL
MOUNTAINS THIS EVENING AND OUTFLOW BOUNDARY INTERACTION MAY KEEP
SOME LIGHT SHOWERS GOING BEYOND SUNSET. CLOUD TOPS DO NOT APPEAR
TO GET COLD ENOUGH FOR LIGHTNING.

THE NEW AIR MASS IS DRIER AND SLIGHTLY COOLER OVER THE NORTHERN
AND CENTRAL ZONES. SO SUNDAY AFTERNOON ISOLATED TO SCATTERED
SHOWERS WILL BE ALONG AND SOUTH OF THE STALLED FRONT FROM THE
ABAJOS-SAN JUANS SOUTHWARD. SNOW LEVELS IN THE VICINITY OF THE
FRONT...BOTH THIS AFTERNOON NORTH AND SUNDAY AFTERNOON SOUTH...LOOK
TO BE ABOVE THE HIGHEST MOUNTAIN TOPS AS 700MB TEMPS ARE 6 TO 8C.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 354 AM MDT SAT MAR 28 2015

THE EXTENDED PERIOD IS ONE OF TRANSITION TO ZONAL FLOW AND A
HIGHER DEGREE OF UNCERTAINTY. THE MODELS ARE HAVING SOME DIFFICULTY
PROJECTING THE MOVEMENT AND STRENGTH OF SMALL AMPLITUDE
FEATURES...WITH THE ECMWF SHOWING A BIT MORE RUN-TO-RUN
CONSISTENCY.

SUNDAY NIGHT THROUGH MONDAY NIGHT STARTS IT OFF WITH A BROAD FLAT
RIDGE OVER THE WESTERN U.S. THE GFS SHOWS A SHORTWAVE TROUGH
CUTTING THROUGH THE RIDGE AND PRODUCING A BIT OF PRECIP OVER THE
GREAT BASIN AND CENTRAL ROCKIES. THE EC BARELY HINTS AT THIS
FEATURE.

A PROGRESSIVE RIDGE TRAVELS OVER THE AREA TUE...THEN TUE NIGHT
AND WEDNESDAY A STRONG TROUGH IS PROJECTED INTO THE REGION. THE
GFS AND ECMWF ARE IN BETTER AGREEMENT THIS PERIOD AS BOTH KEEP
MOST OF THE MOISTURE NORTH OF THE AREA...BUT BRING IN A STRONGER
WIND BAND. A GENERALLY DRY WESTERLY JET WILL REMAIN OVER THE AREA
THROUGH THURSDAY MORNING IN THE GFS. THU AFTERNOON AND FRI THE GFS
MOVES A WEAK TROUGH ACROSS SOUTHERN WY AND NORTHERN CO. DURING THE
SAME PERIOD THE EC DIGS A STRONGER TROUGH OVER THE GREAT BASIN
THEN PUSHES IT ACROSS THE FORECAST AREA THU AND FRIDAY...WITH NO
GOOD WAY TO TELL WHICH MODEL IS LEANING THE RIGHT WAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 354 AM MDT SAT MAR 28 2015

VFR CONDITIONS WILL DOMINATE INTO SUNDAY MORNING. BRIEF
EXCEPTIONS MAY BE AFTER 22Z AS ISOLATED TO SCATTERED SHOWERS FORM
OVER THE NORTHERN MTNS AND COLORADO CENTRAL MTNS. THE MAIN THREAT
WILL BE POSSIBLE GUSTY ERRATIC OUTFLOW WINDS AT TAF SITES KVEL
KEGE KASE BETWEEN 00Z-04Z. ELSEWHERE KCAG KHDN KSBS COULD SEE
VRB15G35KT CIGS 030-050 IN -SHRA BETWEEN 00Z-04Z. MODERATE MTN TOP
LEVEL TURBULENCE EXPECTED AFT 15Z TODAY...STRONGEST NORTH. ERRATIC
STRONG GUSTS EXPECTED VICINITY AFTERNOON-EVENING BUILDUPS.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&

$$

SHORT TERM...JOE
LONG TERM...CC
AVIATION...JOE



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